Fuel cells are power generation apparatuses utilizing a power generation scheme by electrochemical reaction, and have characteristics such as superior power generation efficiency and environmental response. Among these, a solid oxide fuel cell (hereinafter referred to as an “SOFC”) is a fuel cell in which ceramics, such as zirconia ceramics, is used as an electrolyte, and that is operated using town gas, natural gas, petroleum, methanol, coal gasification gas, etc. as fuel. Such SOFC can generate power with high power generation efficiency by constructing a combined power generation system combining with an internal combustion engine, such as a micro gas turbine (hereinafter referred to as an “MGT”) (refer to the following PTL 1). Specifically, exhaust fuel gas discharged from the SOFC is burned by a combustor, a turbine is driven by combustion gas, and power is generated. As for the combined power generation system, a conventional technology as shown below has been known.
The following PTL 2 discloses that in an air supply apparatus that is installed in a fuel cell power generation plant, and supplies air to a fuel cell, a control amount of a combustion air flow adjustment valve that adjusts a flow rate of supply air is fluctuated, and control action at the time of activation is stabilized.
The following PTL 3 discloses that in activation in a combined power generation system of a solid oxide fuel cell and a gas turbine, a pressure is raised while holding a differential pressure between a fuel side and an air side of the fuel cell within a management value, and that the pressure is raised within a range where differential pressure control follows.